2022年1月11日 (火) 10:30-
Speaker：Ivan I. Smalyukh 氏 (University of Colorado)
Topological order and phases represent an exciting frontier of modern
research . Starting with Gauss and Kelvin, knots in fields, like the
magnetic field, were postulated to behave like particles. However,
experimentally they were found only as transient features and could not
self-assemble into three-dimensional crystals. I will describe
energetically stable solitonic knots that emerge in the physical fields of
chiral liquid crystals and magnets [2,3]. While spatially localized and
freely diffusing in all directions, they behave like colloidal particles
and atoms, self-assembling into crystalline lattices with open and closed
structures, as well as forming low-symmetry mesophases and gas- or
liquid-like states . A combination of energy-minimizing numerical
modeling and nonlinear optical imaging uncovers the internal structure and
topology of individual solitonic knots and the various hierarchical
crystalline and other organizations that they form. Being classified as the
elements of the third homotopy group of two-spheres, these solitonic knots
are robust and topologically distinct from the host medium, though they can
be morphed and reconfigured by weak stimuli like electric or magnetic
fields. I will show how low-voltage electric fields can switch between the
heliknoton [2,3] and hopfion  embodiments of such knot solitons while
preserving their topology. Finally, I will discuss how this emergent
paradigm of knotted solitonic matter could allow for imparting new
designable material properties and for realizing phases of matter that so
far could not be found in naturally occurring materials [5-7].
1. I. I. Smalyukh. Rep. Prog. Phys. 83, 106601 (2020).
2. J.-S. B. Tai and I. I. Smalyukh. Science 365, 1449 (2019).
3. R. Voinescu, J.-S. B. Tai and I. I. Smalyukh. Phys Rev Lett 125, 057201
4. P. J. Ackerman and I. I. Smalyukh. Nature Materials 16, 426 (2017)
5. H. Mundoor, S. Park, B. Senyuk, H. Wensink and I. I. Smalyukh. Science
360, 768 (2018).
6. Y. Yuan, Q. Liu, B. Senyuk and I.I. Smalyukh. Nature 570, 214 (2019).
7. H. Mundoor, J.-S. Wu, H. Wensink and I.I. Smalyukh. Nature 590, 268